Arrangement for igniting controlled rectifiers with the aid of pulses



' J n 17, 967 'WS'CHUTTE 3,299,318

ARRANGEMENT FOR IGNITING CONTROLLED RECTIFIERS WITH THE AID OF PULSESFiled Nov. 25, 1964 5 Sheets-Sheet 1 INVENTOR.

WERNER SCHUTTE AGENT Jam, 17, 1967 1 w.. SCHUT'TE 3,299,318

- Filed Nov. 25, 1964 ARRANGEMENT FOR IGNITING CONTROLLED RECTIFIERSWITH THE AID OF PULSES v 3 Sheets-Sheet 2 VF-D INVENTOR.

WERNER SCHUTTE BY 7 W K AGENT United States Patent 3,299,318 ARRANGEMENTFOR IGNITING CONTROLLED RECTIFIERS WITH THE AID 0F PULSES WernerSchiitte, Hamhurg-Niendorf, Germany, assignor to North American PhilipsCompany, Inc., New York,

N.Y., a corporation of Delaware Filed Nov. 25, 1964, Ser. No. 413,905Claims priority, application Germany, Dec. 13, 1963,

11 Claims. (a. 315-168) inductor, an ohmic resistor and a rectifier toan AC.

voltage source and deriving the pulsatory voltage from the rectifier orfrom the series-combination of the rectifier and the ohmic resistor.However, since neither the ohmic resistance, nor the inductance can "bemade zero, this known phase-shifting device can be adjusted neither to 0nor to 90. From this it follows that the angular range of the ignitionis less than 90 and the output current of the controlled rectifier canbe varied only from approximately 50% to 100%.

However, it is often necessary to control the current from zero to amaximum value. However, this requires an angular range of ignition whichlies between 0 and 180".

To obtain an ignition angle from 0 to 180, it is also already known touse a pulse former stage having an adjustable response threshold or atrigger circuit followed by a differentiating transformer, which iscontrolled by a variable direct voltage or a sinusoidal voltagesuper-imposed on the said direct voltage and shifted in phase by 90 withrespect to the alternating anode voltage of the rectifier.

When the sum of the direct voltage and the instantaneous value of thealternating voltage reaches the trigger threshold, the trigger suppliesan igniting pulse to the rectifier through the transformer.

To permit the ignition angle to be adjusted between 0 and 180 by meansof the direct voltage, the threshold of the trigger and the peak valueof the alternating voltage must be the same and not more than half themaximum direct voltage.

Because of differences in the manufacture of the transformer and becauseof tolerances in the resistors used for the voltage divider in thetrigger, it is unavoidable that the voltage of the trigger becomessmaller or greater than the alternating voltage.

If the voltage of the trigger is too low, the threshold of the triggeris no longer reached at 0 and the igniting pulse is just then notestablished when the full current is required by the rectifier on theground of a control or regulating command. Furthermore, an ignitionangle of 180 cannot then be obtained. If the alternating voltage is toohigh, the ignition angle can be adjusted neither to 0 nor to 180.

It is therefore necessary for each apparatus to be adjusted duringmanufacture.

In an arrangement according to the invention, these disadvantages areavoided by deriving a 90 leading voltage from an alternating voltage ofthe same phase as the alternating anode voltage of the rectifier,preferably by means of a phase-shifting device. In addition a voltagederived from the same voltage source by means of a phase-shifting deviceand lagging by 15 is superimposed, after half-wave rectification ontosaid leading voltage. In known manner, a variable direct voltage issuperimposed on the resulting alternating voltage.

In order that the invention may be readily carried into effect, it willnow be described in detail, by way of example, with reference to theaccompanying diagrammatic drawings, in which:

FIGURE 1 shows a circuit of the arrangement according to the invention;

FIGURE 2 shows a vector diagram of the alternating voltages occurring inthe said circuit;

FIGURE 3 shows the voltages set up at the terminals of the circuit ofFIGURE 1, and.

FIGURE 4 shows the condition occurring :at alternating voltages and/ ortrigger voltages which are 5% higher or lower.

Referring now to FIGS. 1 and 2, a voltage U is applied to thetransformer which is in phase with the alternating anode voltage of thecontrolled rectifier tube, not shown. A series circuit comprisingresistor 2, capacitor 3 and resistor 1 is connected across the secondarywinding of the transformer. A resistor 5 and a diode 4 are seriallyconnected between the center tap A of the transformer secondary and apoint B in the above-mentioned series circuit. The current I flowing inthe series circuit leads the transformer secondary voltage U. Thevoltage drop across resistors 1 and 2 is in phase with the current I andis shown in FIG. 2 by the vectors U and U The voltage across capacitor 3lags the current I by degrees and is represented by the vector U,. Thecircuit is designed so that the voltage across the point A-E lags thesecondary voltage U by approximately 15 degrees. A 90 leading voltage(see FIG. 2) is set up between points A and D of the phase-shiftingdevice comprising resistors 1, 2 and a capacitor 3. This voltage servesfor the vertical control of the trigger and on which is superimposed,after rectification by means of the diode 4, the 15 lagging voltage setup between points A and E.

FIGURE 3 shows the two components of voltage separately, as well as thetotal voltage between points D and F compared with the controlledrectifier anode voltage. As can be seen from this figure, thecombination of the leading voltage, V,, and the rectified laggingvoltage, V produce a control voltage, V having a sharply increased slope(compare the heavy line portion of the curve V with the dashed lineportion). A more reliable and accurate trigger voltage is therebyachieved. The end of the superimposed phase, indicated bycross-hatching, prevents the igniting pulse from passing over at thebeginning of the angular range of ignition. The nominal value of thetrigger voltage may thus be chosen so that the 5% higher triggervoltage, due to the 5% lower alternating voltage, is just reached withcertainty (FIGURE 4).

If the smallest trigger voltage and the highest alternating voltagehappen to coincide, the deviation of the ignition angle with respect tothe first extreme case is comparatively small because of the greaterslope of the curve.

The maximum value of both voltages together, when correctlyproportioned, cannot exceed the maximum direct voltage so that theignition angle of is invariably obtained.

The variable direct voltage necessary for adjusting the ignition .angleis superimposed on the alternating voltage applied to terminals D-F(FIGURE 1), which direct voltage may be derived from, for example, adirect-voltage source 6 through a potentiometer 7. The sum of the directand alternating voltage is thus set up before terminals F and G.Terminals F and G are connected across e: the cathode and controlelectrode of the controlled rectifier to control the firing anglethereof. As a matter of fact, the phase-shifted voltages can be derivedfrom two separate phase-shifting devices.

If the arrangement is part of a control system or the like, the directvoltage is preferably constituted by the output voltage of theregulator. As .an alternative, it can be derived from, for example, aremote resistor.

What is claimed is:

1. A control circuit for a controlled rectifier of the type having ananode, a cathode, and a control electrode, comprising means for applyingan A.C. supply voltage to the anode-cathode path of said controlledrectifier, means for deriving an A.C. voltage which leads said A.C.supply voltage by approximately 90 degrees, means for deriving an A.C.voltage which lags said A.C. supply voltage by approximately 15 degrees,means for rectifying the lagging voltage to obtain a rectified half-wavevoltage, means for combining said lagging rectified voltage and saidderived leading A.C. voltage to produce a control voltage, a source ofdirect voltage, and means for supplying said control voltage and saiddirect voltage to said control electrode so as to control the conductionof said controlled rectifier.

2. A control circuit for a controlled rectifier of the type having ananode, cathode, and a control electrode, said circuit comprising asource of alternating voltage coupled to the anode-cathode path of saidcontrolled rectifier, means for deriving a first A.C. voltage whichleads said alternating voltage by approximately 90 degrees and a secondA.C. voltage which lags said alternating voltageby approximately 15degrees, half-wave rectifier means arranged to rectify said secondvoltage to obtain a rectified half-wave voltage, means for combiningsaid half-wave voltage and said first A.C. voltage to produce a leadingvoltage having a portion of its waveform distorted, means for producinga variable direct voltage, means for combining said direct voltage withsaid distorted leading voltage to obtain a composite control voltage,and means for applying said control voltage between said cathode andsaid control electrode of said controlled rectifier.

3. A circuit as described in claim 2 wherein said voltage deriving meanscomprises first and second phase shifting means for deriving saidleading and lagging voltages, respectively, from said alternatingvoltage source.

4. A circuit as described in claim 3 ilurther comprising control circuitmeans for delivering a control output voltage and means for derivingsaid variable direct voltage from said control circuit means outputvoltage.

5. A control circuit for a controlled rectifier of the type having ananode, cathode, and a control electrode, said circuit comprising meansfor supplying an alternating voltage across the anode and cathode ofsaid controlled rectifier, means for deriving first and second A.C.voltages which lead and lag said alternating voltage by approximately 90degrees and 15 degrees, respectively, means for rectifying said secondA.C. voltage to obtain a rectified half-wave voltage, means forcombining said rectified half-wave voltage and said first A.C. voltageso as to produce a composite alternating voltage which leads said firstmentioned alternating voltage, means for producing a direct voltage,means for combining said direct voltage and said composite alternatingvoltage to obtain a control voltage, and means for supplying saidcontrol voltage to said controlled rectifier control electrode so as tocontrol the conduction period thereof.

6. A circuit as described in claim 5 wherein the magnitude of saiddirect voltage is adjustable to vary the controlled rectifier bias levelto control said conduction period and wherein said A.C. voltage derivingmeans comprises phase shifting means coupled to an alternating voltagesource which is in phase with the alternating volt- 4 age supplied tosaid controlled rectifier anode and cathode.

7. A control circuit for a controlled rectifier of the type having ananode, cathode, and a control electrode, said circuit comprising meansfor supplying an alternating voltage across the anode and cathode ofsaid controlled rectifier, means for deriving from said alternatingvoltage supplying means first and second A.C. voltages which lead andlag said alternating voltage by approximately degrees and 15 degrees,respectively, means for rectifying said second A.C. voltage to obtain arectified half-Wave voltage, means forderiving a variable directvoltage, means for combining said rectified halfwave voltage, said firstA.C. voltage and said variable direct voltage to obtain a controlvoltage which leads said alternating voltage, and means for supplyingsaid control voltage to said controlled rectifier control electrode soas to control the conduction period thereof.

8.A control circuit for a controlled rectifier of the type having ananode, cathode, and a control electrode, said circuit comprising asource of alternating voltage coupled to the anode-cathode path of saidcontrolled rectifier, means for deriving a first A.C. voltage whichleads said alternating voltage by approximately 90 degrees .and a secondA.C. voltage which lags said alternating voltage by approximately 15degrees, means for rectiflying said second A.C. voltage to obtain arectified half-wave voltage, means for vectorially combining saidrectified half-wave voltage and said first A.C. voltage to produce analternating control voltage having a portion of its waveform distorted,and means for supplying said control voltage to said control electrodeof the controlled rectifier.

9. A circuit as described in claim 8 further comprising means forsupplying a variable direct voltage to said control electrode to adjustthe bias level thereof and wherein said control voltage is distorted soas to increase the slope of a portion of its waveform.

10. A control circuit for a controlled rectifier of the type having ananode, cathode, and a control electrode, said circuit comprising asource of alternating voltage coupled across the anode and cathode ofsaid controlled rectifier, a transformer having a primary windingadapted to be connected to an alternating voltage which is in phase withsaid alternating voltage source and a center tapped secondary winding, afirst series circuit comprising resistance and capacitance meansconnected across said secondary Winding to draw a leading current, asecond series circuit comprising a resistor and diode connected betweensaid center tap and a junction point of said first series circuit suchthat the voltage across said second series circuit lags the secondaryvoltage by approximately 15 degrees, a first output terminal connectedto a second junction point of said first series circuit at which thevoltage with respect to said center tap leads by approximately 90degrees, a second output terminal connected to a junction point of saidresistor, and means for coupling said output terminals to the cathodeand control electrode of said controlled rectifier.

11. A circuit as described in claim 10 further comprising means forsupplying a variable direct voltage to said control electrode to adjustthe bias level thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,946,942 7/1960Peck 315194 FOREIGN PATENTS 555,175 11/1957 Belgium.

JOHN W. HUCKERT, Primary Examiner. D. O. KRAFT, Assistant Examiner.

1. A CONTROL CIRCUIT FOR A CONTROLLED RECTIFIER OF THE TYPE HAVING ANANODE, A CATHODE, AND A CONTROL ELECTRODE, COMPRISING MEANS FOR APPLYINGAN A.C. SUPPLY VOLTAGE TO THE ANODE-CATHODE PATH OF SAID CONTROLLEDRECTIFIER, MEANS FOR DERIVING AN A.C. VOLTAGE WHICH LEADS SAID A.C.SUPPLY VOLTAGE BY APPROXIMATELY 90 DEGREES, MEANS FOR DERIVING AN A.C.VOLTAGE WHICH LAGS SAID A.C. SUPPLY VOLTAGE BY APPROXIMATELY 15 DEGREES,MEANS FOR RECTIFYING THE LAGGING VOLTAGE TO OBTAIN A RECTIFIED HALF-WAVEVOLTAGE, MEANS FOR COMBINING SAID LAGGING RECTIFIED VOLTAGE AND SAIDDERIVED LEADING A.C. VOLTAGE TO PRODUCE A CONTROL VOLTAGE, A SOURCE OFDIRECT VOLTAGE, AND MEANS FOR SUPPLYING SAID CONTROL VOLTAGE AND SAIDDIRECT VOLTAGE TO SAID CONTROL ELECTRODE SO AS TO CONTROL THE CONDUCTIONOF SAID CONTROLLED RECTIFIER.